“We weren’t sure if riding would help Scarlett with her disabilities, but she really loves going and giggles away when she is on the horse, especially when they start trotting," said Justin.

"The exercise of riding really helps strengthen her body and she is better both physically and emotionally as a result.”

As a pupil at Welcombe Hills School, Stratford-upon-Avon, Scarlett’s horse riding is a massive therapeutic boost to the youngster who suffers from a unique chromosome re-arrangement which so far remains a mystery to doctors.

“Amazingly during the sessions she understand the words “walk on” so she makes a click click sound with her mouth and afterwards she’s really calm and happy. It’s unbelievable the bond that she and Marco have made together,” said Justin.

Although Scarlett isn’t featured on the stamps that went on sale on Tuesday, Royal Mail chose Compton Verney for its regional launch of a six stamp set entitled Working Horses and Scarlett was on hand to help out with her best mate Marco.

The set features horses from the Riding for the Disabled Association, The King’s Troop Ceremonial Horses, Dray Horses, Royal Mews Carriage Horses, Police Horses and a Forestry Horse.

The Riding for the Disabled Association organises horse events including riding and carriage driving, so that 30,000 people with disabilities can enjoy the activities each year.